In this section the previous work done in the field of Reverse Engineering, relevant to present work is reviewed. Joel Bisson of Vitana Corporation, in his presentation has described the different scanners. He has explained how this scanned data can be used for inspection. This inspection may be Part to CAD inspection or Part to Part inspection. He says that at the time of inspection the location of co-ordinate system becomes irrelevant. Since the best fitting algorithm is based on the relative position of the data and not on its absolute position. He has also given the comparison in between the laser scanners and contact scanners [Bisson98].
Ben Steinberg, Anshuman Razdan, and Gerald Farin in their paper have suggested a method of surface reconstruction with little interaction from user. B-spline surfaces of any degree can be produced and number of segments, tolerances etc. can also be chosen as parameters to the system. The combination of the least-square method, smoothing functions and automated data parameterization conversion produces extremely accurate B-spline surfaces[Razdan98].
Guo suggested a method which generates a parametric surface in two steps: in the first step, we have to construct a simplified surface is constructed, which captures the topological structure of a given object by the use of 3D alpha shapes and in the second step, build a curvature continuous surface is built based on this structure. But the concept of 3D alpha shapes has a few restrictions, such as in a set of data points, no four points lie on a common plane; no five points lie on a common sphere; and for any fixed alpha, the smallest sphere through any 2,3 or 4 points of a given set has a radius different from alpha[Gou97].
The paper presented by Sarkar and Menq on smooth surface approximation gives a nice overview of a method to approximate 3D data by parametric surfaces. The procedure begins with the division of whole array of data points into regions, according to shape change detection. In each region, points are parameterized and knots are selected. Smooth surface approximation is obtained by least-square fitting of B-splines[Sarkar91].
Keytack H., Abella, Robert J., James M., have suggested the integration
of CMM with CAD/CAM for existing parts without drawings. They say that
scanned data can be used as input to the CAD/CAM system for generating
a necessary tool path in reproducing the part. They have given a case study
to define the requirements to complete the cycle from the original part
to the reproduced part[Keytak89].
